I don’t think a puritanical work ethic necessarily is unhealthy, but in your example I would consider the guilt aspect to be.

In your example puritanical work ethic + (irrational imo) guilt = you exceed your contractual requirements to deliver work to your employer.

Keep the work ethic but take the guilt out and perhaps instead you’d meet but not exceed your contractual obligations to your employer, and then organise the rest of your time around industriously working on something else that you’re personally passionate about.

The second example could be unhealthy depending on how you approached it, but I wouldn’t say that it necessarily is, and I would say that it’s a big improvement over the first example.